Department of General Microbiology, Institute of Microbiology and Genetics, Georg-August University of Göttingen, Göttingen, Germany.
Infect Immun. 2013 Mar;81(3):896-904. doi: 10.1128/IAI.01212-12. Epub 2013 Jan 7.
Mycoplasma pneumoniae, the causative agent of atypical pneumonia, is one of the bacteria with the smallest genomes that are nonetheless capable of independent life. Because of their longstanding close association with their human host, the bacteria have undergone reductive evolution and lost most biosynthetic abilities. Therefore, they depend on nutrients provided by the host that have to be taken up by the cell. Indeed, M. pneumoniae has a large set of hitherto unexplored transporters and lipoproteins that may be implicated in transport processes. Together, these proteins account for about 17% of the protein complement of M. pneumoniae. In the natural habitat of M. pneumoniae, human lung epithelial surfaces, phospholipids are the major available carbon source. Thus, the uptake and utilization of glycerol and glycerophosphodiesters that are generated by the activity of lipases are important for the nutrition of M. pneumoniae in its common habitat. In this study, we have investigated the roles of several potential transport proteins and lipoproteins in the utilization of glycerol and glycerophosphodiesters. On the basis of experiments with the corresponding mutant strains, our results demonstrate that the newly identified GlpU transport protein (MPN421) is responsible for the uptake of the glycerophosphodiester glycerophosphocholine, which is then intracellularly cleaved to glycerol-3-phosphate and choline. In addition, the proteins MPN076 and MPN077 are accessory factors in glycerophosphocholine uptake. Moreover, the lipoproteins MPN133 and MPN284 are essential for the uptake of glycerol. Our data suggest that they may act as binding proteins for glycerol and deliver glycerol molecules to the glycerol facilitator GlpF.
肺炎支原体是引起非典型肺炎的病原体，是能够独立生活的最小基因组细菌之一。由于它们与人类宿主长期密切相关，细菌经历了简化进化，失去了大多数生物合成能力。因此，它们依赖于宿主提供的营养物质，这些营养物质必须被细胞吸收。事实上，肺炎支原体有一大组尚未被探索的转运蛋白和脂蛋白，它们可能参与了运输过程。这些蛋白质加起来约占肺炎支原体蛋白质含量的 17%。在肺炎支原体的自然栖息地，人类肺上皮表面，磷脂是主要的可用碳源。因此，甘油和甘油磷酸二酯的摄取和利用对于肺炎支原体在其常见栖息地的营养非常重要。在这项研究中，我们研究了几种潜在的转运蛋白和脂蛋白在甘油和甘油磷酸二酯利用中的作用。基于相应突变株的实验，我们的结果表明，新鉴定的 GlpU 转运蛋白（MPN421）负责甘油磷酸二酯甘油磷酸胆碱的摄取，然后在细胞内裂解为甘油-3-磷酸和胆碱。此外，蛋白质 MPN076 和 MPN077 是甘油磷酸胆碱摄取的辅助因子。此外，脂蛋白 MPN133 和 MPN284 对甘油的摄取是必不可少的。我们的数据表明，它们可能作为甘油的结合蛋白，并将甘油分子输送给甘油促进剂 GlpF。
